Best name for PDP-11/05-10

Noel Chiappa jnc at
Fri Feb 26 08:04:30 CST 2016

    > From: Mattis Lind

    > The NC is in the BA11-D 10 1/2 inch box. It uses the H750 PSU.

Odd. I have an -11/10 in a 10-1/2 box with an H750; the metal plate on the
back of the box just says "PDP 11-10" (well, the '-' is actually a dot, at
the level of the '-'). No 'NC'. I wonder if that's a configuration
designator, not a model?

{At this point, IRL, I did a whole lot of reading and looking.}

I looked in some old PDP-11/05-10 price lists... (More "11/21"s... :-), and
did find some -11/05 models with pretty large alphabetic model designators,
e.g. "11/05-LB", but no "11/10-NC". However, the "Options and Modules List"
online from June, 1974 _does_ list the "11/10-NC" - it describes it as
"KD11-B, BA-11DC 10.5 INCH BOX, MM11-L, KY11-JE, CONFIG 4, 115V". There's
also an "11/05-NC", the same except for a "KY11-JD" (that must be for the
different number printed on the faceplate). No idea what the "CONFIG 4"

However, the real victory came when looking in my just-acquired copy of
DEC-11-H05AA-B-D.pdf. I see it also includes a "DEC-11-H05AA-B-D Supplement
1", which is the "PDP-11/05, 11/10 10 1/2 inch mounting box and power system"
- and that _does_ describe the NC/ND (120V/240V). And those have a slightly
different backplane (below) from the ones described in DEC-11-H05AA-A-D; so
that's a fourth model of -11/05-10 backplane - and it does differentiate
the -11/05N-10N (as I will call them) from the others.

    > I have three machines with three different backplanes. One 11/05-NC,
    > one 11/10 in 5.25 inch box and one 11/05-S in BA11-K.

What kind of backplane does the second one have; one of the 2xMM11-L CPU
backplanes (one with, and one without, an SPC slot), or the 1xMM11-L?

    > NC can have two MM11-L. No SPC slots.

Got it. I was very confused, because the 11/05-10 manual (DEC-11-H05AA-A-D)
says that the 2xMM11-L backplane has one SPC slot (the last one, IIRC).
However, as noted, the -11/05N-10N apparently has a different backplane, to
accomodate the M9970 dual console serial line connector card. (That backplane
isn't documented in the DEC-11-H05AA-A-D -11/05-10 manual I'd been looking at
- that manual doesn't show a space on the 2xMM11-L backplane for that card).
However, the later "PDP-11/05, 11/10 10 1/2 inch mounting box and power
system" manual _does_ describe it; and in adding a slot for the M9970, they
lost the SPC slot in the 2xMM11-L backplane.

So I guess that's the one you're talking about here?

    > From: Bill Degnan

    > The more useful box is the S model because the more standard enclosure
    > can be used for testing other UNIBUS cards more easily or than parity
    > RAM.

?? How is is better? The BA11-D box will hold hex cards? Or are the SPC slots
in the 11/05-10S backplane MUD slots? Or is it just that the BA11-K will hold
DD11-C/D backplanes, with MUD slots? (I don't know if there are any MUD
backplanes that go into the BA11-D - at least without a hand-mod to the power


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